1. Field of the Invention
This invention relates to a structure and a manufacturing method of a plasma display panel (hereinafter, referred to as “PDP”), and more particularly, relates to a structure and a manufacturing method of a PDP that causes no bubbles in a dielectric layer of a glass material used for covering metal electrodes.
2. Description of the Related Art
An AC drive three-electrode face discharge type PDP has been known as a conventional PDP. This PDP has a structure in which a number of display electrodes capable of face discharging are placed in a horizontal direction on the inner face of a substrate on the front face side, and a number of address electrodes used for selecting a light-emitting cell are placed on the inner face of a substrate on the back face side, with an intersection between each display electrode and each address electrode serving as one cell (unit light-emitting area). One pixel is constituted by three cells, that is, a red color (R) cell, a green color (G) cell and a blue color (B) cell.
The substrate on the front face side and the substrate on the back face side, thus formed, are placed face to face with each other with the peripheral portion being sealed, and the inside thereof is then filled with a discharge gas so that the PDP is manufactured.
In the above-mentioned PDP, upon forming the substrate on the front face side, a plurality of display electrodes are formed on a glass substrate. These display electrodes are normally constituted by transparent electrodes and metal electrodes.
The transparent electrodes are formed by film-forming ITO, SnO2 or the like on the substrate and by patterning the resulting film.
The metal electrodes are used for reducing the wiring resistance of the electrodes, and also referred to as bus electrodes. The metal electrodes are formed as metal electrodes having a three-layer structure through processes in which metal films of three layers of Cr—Cu—Cr are formed on the transparent electrodes and the resulting films are patterned. Alternatively, a silver paste is applied onto the transparent electrodes and then subjected to a firing process so that the metal electrodes are formed.
After the display electrodes have been formed in this manner, a dielectric layer is formed on the display electrodes, and a protective layer is then formed thereon.
Upon forming the substrate on the back face side, address electrodes made of metal are formed on a glass substrate in a direction crossing the display electrodes, and a dielectric layer is formed thereon, with barrier ribs being formed thereon, and a phosphor layer is then formed in an elongated recess groove between the barrier ribs.
With respect to the material for the dielectric layer, normally, a low-melting-point glass containing lead is normally used because of its easiness in processability (see Japanese Unexamined Patent Publication No. Hei 6(1994)-33503).
In recent years, however, non-lead structures for domestic electric appliances have been developed so as to reduce the environmental load, and in the field of the PDPs also, there have been strong demands for non-lead materials.
However, in the case when a dielectric layer is formed by placing a glass material and firing the material, upon application of a non-lead-based material as the glass material, the glass softening point becomes higher, causing degradation in the glass flowability upon firing the glass material. As a result, bubbles, generated from the glass material during the firing process due to an electrochemical reaction between the metal electrodes and glass, are hardly released during the firing process to remain in the dielectric layer. Product defects, such as an insufficient insulation and a reduction in luminescence due to degradation in the light transmitting property, are caused by the influence of these remaining bubbles (voids).